Applicant claims, under 35 U.S.C. xc2xa7 119, the benefit of priority of the filing date of Feb. 17, 2000 of a German patent application, copy attached, Serial Number 100 07 225.9, filed on the aforementioned date, the entire contents of which is incorporated herein by reference. Applicant also claims, under 35 U.S.C. xc2xa7 119, the benefit of priority of the filing date of Nov. 9, 2000 of a German patent application, copy attached, Serial Number 100 55 488.1, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a position measuring device and to a method for operating a position measuring device.
2. Discussion of Related Art
Known position measuring devices typically include a measuring graduation in a measuring graduation plane as well as a scanning unit movable relative to the measuring graduation. In the scanning unit, the scanning elements by way of whichxe2x80x94as a function of the physical scanning principlexe2x80x94position-dependent output signals are generated are disposed in a scanning plane. The spacing between the measuring graduation plane and the scanning plane will be called the scanning spacing hereinafter. The relative motion between the aforementioned planes or the measuring graduation and the scanning unit can be either linear or rotational as well.
As examples for such position measuring devices, known photoelectric or inductive, incremental position measuring devices can be mentioned, of the kind used in numerically controlled machine tools. In photoelectric position measurement systems, typically various optoelectronic components are disposed in the scanning plane and serve to generate displacement-dependently modulated output signals; these include the light source used and suitable photodetectors. In the case of inductive position measuring devices, planar transmission and/or reception coils, for instance, are disposed in the scanning plane. With regard to inductive position measuring devices, German Patent Disclosure DE 197 51 853 A1 of the present applicant can be referred to. German Patent Disclosure DE 197 51 853 A1 corresponds to U.S. Pat. No. 6,111,402, the entire contents of which are incorporated herein by reference.
One important variable in such position measuring devices is the applicable scanning spacing, which must be set as precisely as possible in the assembly process. This is necessary in order to assure adequately high signal amplitudes for the output signals generated during the measurement operation. The most precise possible setting of the scanning spacing upon assembly is necessary especially in systems that are fully assembled not by the manufacturer but only later by the customer. Typically, such position measuring devices in the case of linear systems are called exposed measurement systems; in the case of rotational systems, they are called modular rotary encoders for integration.
For setting the most optimal possible scanning spacing, many mechanical aids in calibration have already been proposed. A disadvantage of these various aids in calibration that can be named is that they are each suitable only for certain constructions of such a position measuring device and accordingly cannot be employed universally.
Along with a suitable scanning spacing, further variables are significant for optimal functional status during the operation of position measuring devices; these variables too must be optimized as well as possible when operation begins.
An object of the present invention is therefore to disclose a method which can be employed as universally as possible for operating a position measuring device, as well as a suitable position measuring device, which make precise setting of an optimal functional state of the position measuring device possible.
The above object is attained by a method for operation of a position measuring device, which comprises a scanning unit that defines a scanning plane and a measuring graduation that defines a measuring graduation plane, the scanning unit and the measuring graduation are movable relative to one another during a measurement operation, and position-dependent output signals are generated during scanning performed by the scanning unit. The method includes regulating the position dependent output signals to constant signal amplitudes by action on a controlling variable, ascertaining the value of the controlling variable required for the regulating and displaying the value of the controlling variable.
The above object is also attained by a position measuring device for generating position-dependent output signals that includes a scanning element by which a scanning plane is defined and a measuring graduation movable relative to the scanning element and defining a measuring graduation plane. The position measuring device further includes a regulating device for regulating output signals to constant signal amplitudes, in that the regulating device acts upon a predetermined controlling variable, to which end the requisite value of the controlling variable for the purpose of regulating is ascertained continuously by the regulating device.
Both the method and the position measuring device according to the present invention offer a number of advantages in comparison to versions of the prior art.
For instance, the method of the present invention is no longer tied to special mechanical constructions of the applicable position measuring device; instead, it can be employed universally with the most various types of such position measuring devices.
In installation situations that for instance do not permit visual checking of the set scanning spacing, the method of the present invention offers the user reliable information about the currently set scanning spacing. Via suitable calibration elements, the user need then merely set the scanning spacing, predetermined by the manufacturer, in a defined way.
The method of the present invention proves especially advantageous if a regulating device for regulating the output signals to constant signal amplitudes is already provided in the applicable position measuring device. For displaying the current scanning spacing at the time of assembly, then only the value of the controlling variable determined on a continuous basis by the regulating device requires further processing.
The method according to the present invention can furthermore be used in both linear and rotational position measuring devices. The method of the present invention can also be realized in conjunction with position measuring devices that are based on different physical scanning principles. Analogously, it is understood that it is possible to embody the most various position measuring devices in a manner according to the present invention.
Not only the scanning spacing but furthermore the entire functional status of the position measuring device can also be optimized according to the present invention.
Further advantages as well as details of the present invention will become apparent from the ensuing description of an exemplary embodiment in conjunction with the accompanying drawing.